Fuel injection control system for internal combustion engines

ABSTRACT

A fuel injection control system for internal combustion engines, wherein, the fuel supply is adapted to be cut during coasting only if the pressure of air in the engine suction pipe is detected to drop below a certain predetermined value and at the same time the engine throttle is detected either to be moving in the direction of decreasing the degree of opening of the throttle valve or to remain stationary, and the fuel supply is resumed to recover the acceleration of the engine when the throttle starts to move in the direction of increasing the opening of the throttle valve even during the coasting of the engine.

United States Patent Fujisawa 1 June 20, 1972 54] FUEL INJECTION CONTROL SYSTEM 3,430,616 4/1969 Glockler 123/32 FOR INTERNAL COIVIBUSTION 3,463,130 8/1969 Reichardt... 1 23/32 ENGINES 3,515,104 6/1970 Reichardt ..123/32 [72] Inventor: Hideya Fujisawa, Kariya, Japan FOREIGN PATENTS OR P L C TI NS [73] Assignee: Nippondenso Kabushiki Kaisha, Kariya- 1,243,288 1/ 1959 France 123/32 shi, Aichi-ken, Japan Primary ExaminerLaurence M. Goodridge [22] Flled' July 1970 Assistant ExaminerRonald B. Cox [21] Appl No; 52,465 AtrorneyCushman, Darby & Cushman [57] ABSTRACT [30] Foreign Application Priority Data A fuel injection control system for internal combustion en- Aug. 20, 1969 Japan ..44/65906 gines wherein, the fuel Supply is adapted to be cut during coasting only if the pressure of air in the engine suction pipe is [52] US. Cl ..123/32 EA, 123/97 B detected to drop below a certain predetermined value and at [51] Int. Cl ..F02b 3/00, F02d 31/00, F02d 9/00 58 M Sc h 123/32 EC 32 E 97 B the same time the engine throttle 1S detected either to be mov- 1 [e o are ing in the direction of decreasing the degree of opening of the throttle valve or to remain stationary, and the fuel supply is [56] References cued resumed to recover the acceleration of the engine when the UNITED STATES PATENTS throttle starts to move in the direction of increasing the 0pening of the throttle valve even during the coasting of the engine. 2,859,738 11/1958 Campbell. 2,911,966 1 1/1959 Pribble ..123/32 1 Claim, 1 Drawing Figure FUEL INJECTION CONTROL SYSTEM FOR INTERNAL COMBUSTION ENGINES BACKGROUND OF THE INVENTION:

1. Field of the Invention This invention relates to fuel injection control systems having electronically controlled fuel injection means for use in internal combustion engines and, more particularly, a fuel injection control system having an electromagnetic type fuel injector valve, the operation of which is electrically controlled with respect to the operative time thereof to thereby control the fuel injection.

2. Description of the Prior Art The fuel injection control system for controlling the fuel injection means of the type, to which the invention pertains, is usually employed to minimize the fuel consumption and reduce poisonous gases contained in the exhaust gases during the coasting of the engine with the throttle valve closed and at a speed higher than the idling speed (the engine speed when the engine is idling without load) owing to the momentum of the vehicle under such situations as when decelerating the engine and driving down a descent. To this end, detection is made of the pressure in the engine suction pipe so as to cut the fuel supply when the detected pressure gets below a value corresponding to the idling condition of the engine. The detection of the suction pipe pressure to cut the fuel supply is made because of the fact that when the engine is coasting its speed is higher than that when it is idling and the suction pipe pressure is correspondingly higher than that under the idling condition.

With the above described type of the system, however, the fuel supply cannot be immediately resumed when accelerating the engine under the coasting condition, but a time delay is involved. Also, upon resumption of the fuel supply the engine output is suddenly increased giving a shock to passengers upon the acceleration of the vehicle. Thus, the use of this system in automotive engines presents a difficulty in respect of comfortability.

SUMMARY OF THE INVENTION An object of the invention is to provide a fuel injection control system for internal combustion engines for controlling an electromagnetically operated fuel injector valve with respect to the operative time thereof in accordance with the operating parameters of the engine through an electronic control means in such a manner that when the engine throttle is moving in the direction of decreasing the throttle opening or is remaining stationary and at the same time the air pressure in the engine suction pipe becomes lower than the pressure corresponding to the engine idling condition, the pulse width of a square-wave signal delivered from a square-wave producing circuit such as a multivibrator to the fuel injector valve is reduced to zero, thereby cutting the fuel supply to the engine.

According to the invention, excellent effects can be featured, that as the pulse width of the square-wave signal fed from the square-wave producing circuit to the electro-magnetic fuel injector valve is reduced to zero to cut the fuel supply to the engine only when the engine throttle is moving in the direction of decreasing the throttle opening or remains stationary and at the same time an electric signal produced by a detector detecting the engine suction pipe air pressure gets below a predetermined level, the fuel supply may be immediately resumed for accelerating the engine even when the engine is coasting, so that a time delay when accelerating the engine as in the conventional system is eliminated, and that as the fuel supply is resumed when the engine load is low, there is no sudden increase of the engine output upon the resumption of the fuel supply, thus preventing any shock to the passengets.

BRIEF DESCRIPTION OF THE DRAWING The accompanying drawing schematically illustrates the essential part of the fuel injection control system embodying the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The invention will now be described in conjunction with the illustrated embodiment. Reference numeral I designates a suction pipe of the engine. In the suction pipe 1 is disposed a throttle holder pin 2 carrying a throttle 3 secured thereto and a throttle lever 4 also secured thereto. The throttle lever 4 is driven by a link mechanism (not shown) to rotate the throttle holder pin 2 so as to regulate the amount of air supplied to the engine. Provided to the suction pipe 1 is an electromagnetically operated fuel injector valve 5 connected to a fuel duct 6, through which pressurized fuel from a fuel pump (not shown) is supplied. Numeral 7 designates a suction pipe air pressure detector to detect the absolute pressure in the suction pipe 1 through a duct 7a so as to produce a corresponding electric output for impression on a square-wave wave producing circuit 8. The output of circuit 8 is a square-wave as indicated at 9, with its pulse width t proportional to the absolute pressure in the suction pipe 1. During the period of this pulse width r the fuel injector valve 5 is held in the open or operative position, and an amount of fuel proportional to the pulse width r is supplied to the engine. Numeral l0 designates a permanent magnet slidably extending in and along the axis of a surrounding coil 1 1, which is attached at an end by means of a pin 12 to the suction pipe 1. The end of the permanent magnet 10 remote from the coil 11 is tied by a pin 13 to the throttle lever 4.

In operation, when the throttle lever 4 is removed in the direction of arrow 14 (the direction of increasing the throttle opening of the throttle 3), the permanent magnet 10 advances in the direction of arrow 15 into the coil 11. The electromotive force built up in the coil 11 at this time causes current to pass through a diode 16 into the square-wave producing circuit 8. On the other hand, when the throttle lever 4 moves in the direction opposite to the direction of the arrow 14 (the direction of decreasing the throttle opening of the throttle 3), the permanent magnet 10 is driven in the direction opposite to the direction of arrow 15. In this case, current in the coil II, which is opposite in direction to the current in the above case, is blocked by the diode 16. When the throttle lever 4 is stationary, no electromotive force is developed in the coil 11, so no current flows into the square-wave producing circuit 8. If the level of the output of the suction pipe air pressure detector 7 gets below a certain predetermined value when the throttle 3 is either moving in the direction of decreasing the throttle opening or stationary to provide no current through the diode 16 to the square-wave producing circuit 8, a switch provided in the square-wave producing circuit 8, is actuated, thus reducing the pulse width t of the square-wave output 9 to zero to render the electromagnetic fuel injection valve 5 inoperative or closed so as to cut the fuel supply.

As stated earlier, the air presure in the suction pipe varies dependent upon the engine speed and the throttle opening of the throttle 3 such that it is lower during coasting than during idling, so that the coasting condition of the engine may be detected by detecting the suction pipe air pressure. Thus, it is possible to cut the fuel supply only when the throttle 3 is either moving in the direction of decreasing the throttle opening or stationary under the coasting condition of the engine and provide for the supply of fuel when the throttle is moving in the direction of increasing the throttle opening, that is, when the engine is being accelerated, even under the coasting condition. In this manner, the vehicle may be smoothly accelerated without any delay, and a sudden increase of the engine output upon resumption of the fuel supply may be avoided.

I claim:

1. A fuel injection control system for internal combustion engines comprising zero when the engine throttle is either moving in the direction of decreasing the throttle opening or stationary and at the same time the air prewure in the suction pipe becomes lower than the pressure corresponding to the idling condition of said engine.

t i I i 

1. A fuel injection control system for internal combustion engines comprising an electromagnetically operated fuel injector valve, a circuit connected to said valve for producing a square-wave signal to control said fuel injector valve with respect to the operative time of said valve in accordance with operating parameters of the engine, an air pressure detector to detect absolute pressure in suction pipe to produce an electric signal for impression on said square-wave producing circuit, and a throttle motion detector having a permanent magnet linked to a throttle lever and a coil positioned surrounding said magnet for causing the pulse width of said square-wave signal delivered from said circuit to be reduced to zero when the engine throttle is either moving in the direction of decreasing the throttle opening or stationary and at the same time the air pressure in the suction pipe becomes lower than the pressure corresponding to the idling condition of said engine. 